Time Synchronisation of Technology

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Many technologies are reliant and precise, accurate and reliable time. Time synchronisation is vital in many technical systems that we encounter everyday, from CCTV cameras and ATMs to air traffic control and telecommunication systems.

Without synchronisation and accuracy many of these technologies would become unreliable and in could cause major problems, even catastrophic ones in the case of air traffic controllers.

Precise time and synchronisation also plays an increasingly important part in modern computer networking, ensuring the network is secure, data is not lost, and the network can be debugged. Failing to ensure a network is synchronised properly can lead to many unexpected problems and security issues.

Ensuring accuracy

To ensure accuracy and precise time synchronisation modern technologies and computer networks the time controlling Network Time Protocol (NTP) is most commonly employed. NTP ensures all devices on a network, whether they are computers, routers, CCTV cameras or almost any other technology, are maintained at the exact same time as every other device on the network.

It works by using a single time source that it then distributes around the network, checking for drift, and correcting devices to ensure parity with the time source. It has many other features such as being able to assess errors and calculating the best time from multiple sources.

Obtaining the time

When using NTP, getting the most accurate source of time allows you to keep your network synchronised – not just together but also synchronised to every other device or network that uses that same time source.

A global timescale known as Coordinated Universal Time (UTC) is what most NTP servers and technologies use. A sit is a global timescale, and is not concerned with time zones and daylight saving, UTC allows networks across the world to communicate precisely with the exact same time source.

NTP time servers

Despite their being many sources of UTC across the internet, these are not recommended for accuracy and security reasons; to receive an accurate source of NTP there are really only two options: using a NTP time server that can receive radio transmissions from atomic clock laboratories or by using the time signals from GPS satellites.

Windows Server and the Importance of NTP

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Windows Server is the most common operating system used by business networks. Whether it is the latest Windows Server 2008 or a previous incarnation such as 2003, most computer networks used in trade and business have a version.

These network operating systems make use of the time synchronization protocol NTP (Network Time Protocol) to ensure synchronicity between all devices connected to the network. This is vital in the modern world of global communication and trade as a lack of synchronization can cause untold problems; data can get lost, errors can go undetected, debugging becomes near impossible and time sensitive transactions can fail if there is no synchronization.

NTP works by selecting a single time source and it be checking the time on all devices on the network, and adjusting them, it ensures the time is synchronised throughout. NTP is capable of keeping all PCs, routers and other devices on a network to within a few milliseconds of each other.

The only requirement for network administrators is to select a time source – and this is where many IT professionals commonly go wrong.

Internet time servers

Any source of time to synchronize a network to should be UTC (Coordinated Universal Time) which is a global timescale controlled by the world’s most accurate atomic clocks and the number one source for finding a UTC time server is the internet.

And many network administrators opt to use these online time servers thinking they are an accurate and secure source of time; however, this is not strictly the case. Internet time servers send the time signal through the network firewall which means viruses and malicious users can take advantage of this ‘hole.’

Another problem with internet time servers is that their accuracy can’t be guaranteed. Often they are not as accurate as a profession network requires and factors such as distance away from the host can make differences in the time.

Dedicated NTP time server

Dedicated NTP time servers, however, get the time directly from atomic clocks – either from the GPS network or via secure radio transmissions from national physics laboratories. These signals are millisecond accurate and 100% secure.

For anyone running a network using Windows Server 2008 or other Microsoft operating system should seriously consider using a dedicated NTP server rather than the internet to ensure accuracy, reliability and security.

How accurate does NTP Synchronisation need to be?

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Computers advance at a remarkable rate; in effect computers double in power, speed and memory every five years, and with such advances in technology many people assume that the clocks that control the time of a computer are just as powerful.

However, nothing could be further from the truth; most system clocks are crude crystal oscillators that are prone to drift, which is why computer time synchronisation is so important.

In modern computing, nearly every aspect of managing a network is reliant on time. Timestamps are the only frame of reference a computer has to ascertain if an event has occurred, is due to, or shouldn’t occur.

From debugging, to conducting time sensitive transactions over the internet, accurate time is essential. But how accurate does it have to be?

Coordinated Universal Time

Coordinated Universal Time (UTC) is a global timescale derived from atomic clocks. UTC was developed to allow technological devices, such as computer networks, to communicate with a single time.

Most computer networks use time servers governed by NTP (Network Time Protocol) to distribute UTC across the network. For most applications, accuracy to within a few hundred milliseconds is sufficient – but achieving this accuracy is where the difficulty lies.

Getting an accurate source of time

There are several options for synchronizing a network to UTC. Firstly, there is the internet. The internet is awash with time servers that proclaim to supply an accurate source of UTC. However, surveys of these online sources of time indicate that many of them are wholly inaccurate being seconds, minutes and even days out.

And even the most accurate and respected sources from NIST (National Institute of Standards and Time) and Microsoft, can vary depending on the distance your network is away.

Dedicated Time servers

Dedicated NTP time servers use a more direct approach to achieve accurate synchronisation. Using atomic clocks, either from the GPS satellite network or from physics laboratories (like NIST and the UKs NPL); the time is beamed directly to the NTP time server that is connected to the network.

Because dedicated devices like this receive the time directly from atomic clocks they are incredibly accurate, enabling the entire network to be synchronised to within just a few milliseconds of NTP.

NTP Servers versus Internet Time What is the best method for Accurate Time?

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Accurate and reliable time is highly important and as networks and the internet gets faster and faster – accuracy becomes even more essential.

Computers internal clock systems are nowhere near accurate enough for many networked tasks. As simple quartz chronometers they will drift, by as a much as a second which perhaps wouldn’t be a problem if it wasn’t for the fact that all the clocks on the network may drift at different rates.

And as the world becomes more global, ensuring computer networks can talk to each other is also important meaning that synchronisation to the global timescale UTC (Coordinated Universal Time) is now a prerequisite for most networks.

Methods of Synchronisation

There are currently, only two methods for getting truly accurate and reliable time:

  • Use of an internet based time server from places like NIST (National Institute of Standards and Time) or Microsoft.
  • Use of a dedicated NTP time server – that receives external time sources such as from GPS

There are advantages and disadvantages to both types of sources – but which method is best?

Internet Time

Internet time has one great advantage – it is often free. However there are disadvantages to using an internet tie source. The first is distance. Distance across the internet can have a dramatic effect and as the internet gets quicker the distance has an even bigger effect meaning that accuracy become more tenuous.

Another disadvantage of internet time is the lack of authentication and the security risk it poses. Authentication is what the time protocol NTP (Network Time Protocol) uses to establish the true identity of a time source.

Furthermore, an internet time source can only be accessed through a network firewall so a UDP port has to be kept open providing a possible entrance for software nasties or malicious users.

NTP Time Server

NTP time servers on the other hand are dedicated devices. They retrieve a source of UTC externally to the firewall from either GPS or a long wave radio transmission. These come direct from atomic clocks (in the cased of GPS the atomic clock is onboard the satellite) and so can’t be hijacked by malicious users or viruses.

NTP servers are also far more accurate and are not impinged by distance meaning that a network can have millisecond accuracy all the time.

When Time Servers go Bad

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“Time is what prevents everything from happening at once,’ said eminent physicist John Wheeler. And when it comes to computers his words couldn’t be any more relevant.

Timestamps are the only method that a computer has to establish if an event has occurred, is meant to occur or shouldn’t be occurring just yet. For a home PC, the computer relies on the inbuilt clock that displays the time on the corner of your operating system, and for most home uses this is satisfactory enough.

However for computer networks that have to communicate with each other, relying in individual system clocks can cause untold problems:

All clocks drift, and computer clocks are no different and problems occur when two machines are drifting at different rates as the time does not match up. This poses a conundrum for a computer as it is unsure of which time to believe and time critical events can fail to occur and even simple tasks like sending an email can cause time confusion on a network.

For these reasons, time servers are commonly used to receive the time from an external source and distribute it around the network. Most of these devices use the protocol NTP (Network Time Protocol) which is designed to provide a method of synchronising time on a network.

However, time servers are only as good as the time source that they rely on and when there is a problem with that source, synchronisation will fail and the problems mentioned above can occur.

The most common cause for time server failure or inaccuracy is the reliance on internet based sources of time. These can neither be authenticated by NTP nor guaranteed to be accurate and they can also lead to security issues with firewall intrusion and other malicious attacks.

Ensuring the NTP time server continues to get a source of highly accurate time is fairly straight forward and is all a matter of choosing an accurate, reliable and secure time source.

In most parts of the world there are two methods that can provide a secure and reliable source of time:

  • GPS time signals
  • Radio referenced time signals

GPS signals are available anywhere on the planet and are based on GPS time which is generated by atomic clocks onboard the satellites.

Radio referenced signals like MSF and WWVB are broadcast on long wave from physics laboratories like NIST and NPL.

GPS as a Timing Reference for NTP servers

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The GPS system is familiar to most people. Many cars now have a GPS satellite navigation device in their cars but there is more to the Global Positioning System than just wayfinding.

The Global Positioning System is a constellation of over thirty satellites all spinning around the globe. The GPS satellite network has been designed so that at any point in time there is at least four satellites overhead – no matter where you are on the globe.

Onboard each GPS satellite there is a highly precise atomic clock and it is the information from this clock that is sent through the GPS transmissions which by triangulation (using the signal from multiple satellites) a satellite navigation receiver can work out your position.

But these ultra precise timing signals have another use, unbeknown to many users of GPS systems. Because the timing signals from the GPS atomic clocks are so precise, they make a good source of time for synchronising all sorts of technologies – from computer networks to traffic cameras.

To utilise the GPS timing signals, a GPS time server is often used. These devices use NTP (Network Time Protocol) to distribute the GPS timing source to all devices on the NTP network.

NTP regularly checks the time on all the systems on its network and adjusts it accordingly if it has drifted to what the original GPS timing source is.

As GPS is available anywhere on the planet it provides a really handy source of time for many technologies and applications ensuring that whatever is synchronised to the GPS timing source will remain as accurate as possible.

A single GPS NTP server can synchronize hundreds and thousands of devices including routers, PCs and other hardware ensuring the entire network is running perfectly coordinated time.

Synchronizing a PC to an Atomic Clock

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Atomic clocks are without doubt the most accurate time pieces on the face of the planet. In fact the accuracy of an atomic clock in incomparable to any other chronometer, watch or clock.

While an atomic clock will not lose even a second in time in thousands upon thousands of years, you’re average digital watch will perhaps lose a second in just a few days which after a few weeks or months will mean your watch is running slow or fast by several minutes.

The same can also be said for the system clock that controls your computer the only difference is that computers rely even more heavily on time than we ourselves do.

Nearly everything a computer does is reliant on timestamps, from saving work to performing applications, debugging and even emails are all reliant on timestamps which can be a problem if the clock on your computer is running too fast or slow as errors can quite often occur, especially if you are communicating with another computer or device.

Fortunately, most PCs are easily synchronized to an atomic clock meaning they can be accurate as these powerful time keeping devices so any tasks performed by your PC can be in perfect synchronicity with whatever device you are communicating with.

In most PC operating systems an inbuilt protocol (NTP) allows the PC to communicate with a time server that is connected to an atomic clock. In most versions of Windows this is accessed through the date and time control setting (double clicking the clock in the bottom right).

However, for business machines or networks that require secure and accurate time synchronization, online time servers are just not secure or accurate enough to ensure your network is not vulnerable to security flaws.

However, NTP time servers that receive the time direct from atomic clocks are available that can synchronize entire networks. These devices receive a broadcasted timestamp distributed by either national physics laboratories or via the GPS satellite network.

NTP servers enable entire networks to all have exactly synchronized time which is as accurate and secure as is humanly possible.

Synchronizing a Computer Network with a Dedicated Network Time Server

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Synchronization is vital for most computer networks. Timestamps are the only reference a computer can use to analyse when and if processes or applications are completed. Synchronized timestamps are also vital for security, debugging and error logging.

Failure to keep a network adequately synchronized can lead to all sorts of problems. Applications fail to commence, time sensitive transactions will fail and errors and data loss will become commonplace.

However, ensuring synchronization no matter the size of network is straight forward and not costly, thank to the dedicated network time server and the time protocol NTP.

Network Time Protocol (NTP)

NTP has been around even longer than the internet but is the most widely used synchronization protocol available. NTP is free to use and makes synchronization very straight forward. It works by taking a single time source (or multiple ones) and distributes it amongst the network. It will maintain high levels of accuracy even when it loses the original time signal and can make judgements on how accurate each time reference.

NTP Time Server

These come in several forms. Firstly there are a number of virtual time servers across the internet that distributes time free of charge. However, as they are internet based a network is taking a risk leaving a firewall port open for this time communication. Also there is no control over the time signal so if it goes down (or becomes unstable or wholly inaccurate) your network can be left without adequate synchronization.

Dedicated NTP time servers use GPS or radio references to receive the time. This is far more secure and as GPS and radio signals like WWVB (from NIST) are generated by atomic clocks there accuracy is second to none.

Because the NTP protocol is hierarchical it also means that only one dedicated time server needs to be used for a network, no matter the size, as other devices on the network can act as time servers after having rece9ved the time from the primary NTP server.

MSF Downtime on March 11

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The National Physical Laboratory has announced scheduled maintenance this week (Thursday) meaning the MSF60kHz time and frequency signal will be temporarily turned off to allow the maintenance to be conducted in safety at the Anthorn radio Station in Cumbria.

Normally these scheduled maintenance periods only last a few hours and should not cause any disturbance to anybody relying on the MSF signal for timing applications.
NTP (Network Time Protocol) is well suited to these temporary losses of signal and little if no drift should be experienced by any NTP time server user.

However, there are some high level users of network time servers or may have concerns on the accuracy of their technology during these scheduled periods of no signal. There is another solution for ensuring a continuous, secure and equally accurate time signal is always being used.

GPS, most commonly used for navigation and wayfinding it actually an atomic clock based technology. Each of the GPS satellites broadcasts a signal from their onboard atomic clock which is used by satellite navigation devices that work out the location through triangulation.

These GPS signals can also be received by a GPS NTP time server. Just as MSF or other radio signal time servers receive the external signal from the Anthorn transmitter, GPS time servers can receive this accurate and external signal from the satellites.

Unlike the radio broadcasts, GPS should never go down although it can sometimes be impractical to receive the signal as a GPS antenna needs a clear view of the sky and therefore should preferably be on the roof.

For those wanting to make doubly sure there is never a period when a signal is not being received by the NTP server, a dual time server can be used. These pick up both radio and GPS transmissions and the onboard NTP daemon calculates the most accurate time from them both.

A Guide to Synchronising a Network with NTP

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Network Time Protocol (NTP) is a TCP/IP protocol developed when the internet was in its infancy. It was developed by David Mills of the University of Delaware who was trying to synchronise computers across a network with a degree of precision.

NTP is a UNIX based protocol but it has been ported to operate just as effectively on PCs and a version has been included with operating systems since Windows 2000 (including Windows 7, Vista and XP).

NTP, and the daemon (application) that controls it, is not just a method of passing the time around. Any system running the NTP daemon can act as a client by querying the reference time from other servers or it can make its own time available for other devices to use which in effect turns it into a time server itself. It can also act as a peer by collaborating with other peers to find the most stable and accurate time source to use.

One of the most flexible aspects of NTP is its hierarchical nature. NTP divides devices into strata, each stratum level is defined by its proximity to the reference clock (atomic clock). The atomic clock itself is a stratum 0 device, the closest device to it (often a dedicated NTP time server) is a stratum 1 device whilst other devices that connect to that become stratum 2. NTP can maintain accuracy to within 16 stratum levels.

Any network that needs to be synchronised, has to first identify and locate a time source for NTP to distribute. Internet sources of time are available but thee are often taken from stratum 2 devices that operate through the firewall. The only way NTP can peer the time is if the TCP/IP port is left open to allow the traffic through. This could lead to security issues as malicious users can take advantage of this firewall hole.

Dedicated NTP time servers find a source of time via GPS or radio signals and so don’t leave a network vulnerable to attack. By attaching a NTP time server to a router and entire network of hundreds and even thousands of devices can be synchronised thanks to NTP’s hierarchical structure.